Guaranteed atar scores would be calculated based on amount of positions, wouldn't they? The higher the guaranteed atar, the less positions avaliable?
Say it was an atar of 95.00 like you said, only people in the 95th percentile guaranteed a spot and as that is only 5% of the state there should be enough spots to fulfill ALL who get 95.00+?
ATAR cut-offs relect supply and demand more than the intellectual capacity. It varies each year as to how many people apply and how many of those people achieve high atars.
Don't quote me on this, but i believe this is how it works:
For example, say in 2012 5 people were taken into a course and scored these atars respectively:
94.8, 95.2, 96.5, 98.00, 99.95
The cut-off for 2013 would be the person who scored the lowest atar who they let into the course, being 94.8.
In 2013 the cut-off would then be 94.80